Manners, mores and law enforcement have become far less forgiving of sex crimes involving minors in the 31 years since Mr. Polanski was charged with both rape and sodomy involving drugs. He fled rather than face what was to have been a 48-day sentence after he pleaded guilty to unlawful sex with a minor.

But if he is extradited from Switzerland, Mr. Polanski could face a more severe punishment than he did in the 1970s, as a vigorous victims’ rights movement, a family-values revival and revelations of child abuse by clergy members have all helped change the moral and legal framework regarding sex with the young.

Mr. Polanski’s lawyers — including Reid Weingarten, a Washington power player — are likely to argue that Mr. Polanski does not even qualify for extradition from Switzerland, because he was set to be given a jail term of less than one year when he fled to France in 1978.